1. Field of the Invention
The invention relates to an apparatus for massaging the human body with pressurized water jets. More particularly, the invention relates to a full length water-proof bed having an interior chamber with a movable carriage carrying water jets which face upward from beneath the bed.
2. State of the Art
Hydrotherapy has long been accepted as a valuable method of physical and psychological healing. Traditionally, hydrotherapy has been provided in a whirlpool tub or other "wet" environment where pressurized jets of warm water are directed at the body to transmit a massaging effect. Recently, hydrotherapy has been made available in a "dry" environment by providing a waterproof bed with interior water jets. Pressurized water from the interior jets is directed upward against a flexible top surface of the waterproof bed. The bed is typically large enough to support the full length of an adult in the supine or prone position.
One early example of a waterproof bed for hydrotherapy is disclosed in U.S. Pat. No. 4,635,620 to Ricchio. Ricchio teaches a waterbed mattress having a fixed array of upwardly directed water jets arranged along the interior bottom of the mattress. The mattress is filled with water which supports a person on a top membrane of the mattress. Heated pressurized water is directed from the jets toward the top membrane of the mattress. Plumbing associated with the water jets is enclosed in a bed frame which supports the mattress. Ricchio's apparatus provides a relaxing massage for a person lying on the waterbed mattress. However, the points of massage are fixed by the fixed locations of the water jets. In addition, the force of the jets is damped by the water filled mattress since the water exiting the jets must travel through the water in the mattress before striking the top membrane of the mattress.
More recently, it has been known to provide movable water jets beneath a waterproof membrane in order to control the points of massage during hydrotherapy. Hydrotherapy beds with movable water jets are disclosed in U.S. Pat. Nos. 4,757,808 to Effler, Jr., 4,853,988 to Mutzell, and 4,976,256 to Marlin et al. These beds typically include a waterproof bed frame having a water reservoir and an array of upwardly directed water jets mounted on a movable carriage. The carriage is movable by an electromechanical drive mechanism which may include pulleys and cables or gears. A flexible membrane is fitted across the top of the bed frame with a waterproof seal. Unlike Ricchio's waterbed, the flexible membrane in these beds is not supported by water. There is open space between the movable water jets and the flexible membrane so that the jets exert a greater force against the underside of the membrane. While the hydrotherapy beds having movable jets provide much better hydrotherapy than the beds having fixed jets, they are very noisy. When water from the jets strikes a portion or the membrane which is not underlying the person lying on the bed, the force of the water jets (which are typically pulsating) causes the membrane to vibrate. The absence of any damping agent on either side of the membrane permits the vibrating membrane to generate a loud sound. The loud sound is somewhat amplified by reverberation in the open space between the jets and the flexible membrane.
Until now, most of the improvements in hydrotherapy beds with movable water jets have been directed to the electromechanics of moving the jets. Effler, Jr., supra., shows a rather complex worm gear arrangement which moves a carriage back and forth along the length of the bed while simultaneously rotating a pair of water jets. Mutzell, supra., discloses a single movable water jet which is coupled to an indicator arm located over the person lying on the bed. The indicator arm projects a beam of light down onto the person and the single jet is movable in a Cartesian coordinate system to precisely locate the single jet under the person lying on the bed according to the position of the beam of light. Marlin et al., supra., teach a virtually self-supporting membrane beneath which, jets are mounted on a cross member which is movable on parallel tracks by remote control. Position sensors are provided to determine when the cross member is at either extreme end of the tracks, at which time, movement of the cross member is automatically reversed. A microprocessor is included so that the movement of the cross member may be limited to a range within the extreme ends of the track. While Marlin et al. discloses several good "ideas", the details of implementing these ideas are absent from the disclosure. It is unclear how the membrane is mounted and held in place without any underlying support. It is suggested that an optional net be placed under the membrane for further support, but is is not disclosed how the net is mounted. A microprocessor is shown coupled to two extreme position sensors, but it is not disclosed how the microprocessor determines a position other than the extreme positions.
While some of the prior art devices use cables and pulleys to move the water jet(s), others choose a more complex and expensive gear drive arrangement because it is difficult to make the cable and pulley arrangement operate reliably. None of the prior art patents addresses the issue of noise, which is considerable when the space between the water jets and the top membrane is not filled with water.